Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS62 KGSP 290554

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
154 AM EDT Mon May 29 2017

Warm and humid air will remain over our region through at least
Monday, as high pressure settles east of the Florida coast. A cold
front will slowly approach from the northwest, but will struggle to
push through the area in mid week. This front is forecast to
lift north as a warm front late in the week.


As of 1015 PM: Removed remaining mention of convection from
this evening`s forecast. The remainder of the night should be
quiet. Some patchy fog is expected to develop overnight over the
swaths of wet ground following the earlier showers, in addition to
the usual mountain valley fog. With low level flow turning moist
and westerly late tonight over east TN, a small PoP is warranted
along the TN/NC border, but these should be of low impact.

Weak baroclinic zone will remain in place across the region through
the end of the period. Guidance indicates large scale height
falls associated with migration of the central Conus trough should
activate this baroclinic zone by Monday afternoon, as indicated by
increasing deep-layer moisture across the Southeast. Scattered to
numerous convection should therefore initiate across our area,
particularly along the Blue Ridge Monday afternoon. Moderate
instability combined with moderate shear will yield another marginal
threat of severe storms producing large hail and damaging winds
again on Monday. Temperatures will remain above normal through
the period.


As of 230 PM EDT Sunday: The short term begins Monday evening with
large upper high over the western Atlantic, with a deep low over
the Great Lakes and southern Ontario. Southwest flow aloft over the
Southeast and Southern Appalachians will continue bringing a deep
moisture fetch from the western Gulf over the area. Any convection
lingering at the start of the period will slowly sag south overnight
as the trough axis continues to push the wavetrain east. NAM keeps a
minimum of instability across the area with high pressure centered
over the Southeast ridging into the Piedmont, but the GFS is a
little faster with the approaching surface trough, allowing some
minimal instability across the Blue Ridge by midday, traversing into
the Piedmont during the afternoon. Very little shear to work with so
expect generally diurnal convective chances and as is typical cannot
rule out an isolated strong to marginally severe pulse storm, but
not particularly exciting. The upper trough axis pushes closer to
the area Tuesday night into Wednesday, but by Wednesday afternoon
the surface trough axis will have generally pushed through the
forecast area, leaving us in a minimum of instability. Shear will be
increased due to the proximity of the upper trough, but again
convective chances look diurnal at best, and more likely a little
less than. Temperatures through the period pretty close to seasonal
normals, perhaps only a degree or two off.


As of 210 PM Sunday: A broad upper trough remains over the East as a
closed upper low will remain located just north of the Great Lakes
Thursday.  The surface cold front is expected to pass south of our
area early Thursday with transit weak high pressure reaching the
mid Atlantic coast late Thursday. With this high moving offshore and
low level moisture increasing across the Gulf states with SW wind
behind the high, the front moves north as a warm front. This warm
front should reach the Virginias by Sunday and by that time we will
be deep in moist subtropical air. A series of shortwaves will be
advancing across the Plains States to the SE States in combination
with the persistent low level flow from the Gulf will keep a good
chance of convection in the forecast each day. The extensive
cloud cover will result in Max Temps bring held down a bit and Min
Temps being a few degrees above normal. Instability will be rather
low Thursday and then models bring CAPE values up to near 2000 in
the Piedmont over the weekend. As the general broad trough continues
over the East, the upper ridge will remain over the West.


At KCLT: VFR conditions are expected for the most part thru the
period. Because of the rain that fell close to sunset yesterday
evening, there is the potential for a little ground fog around
daybreak. I will add a tempo for 5SM BR. Otherwise, expect just some
thin cirrus and light NW wind thru mid-morning. After that, a
cumulus field is expected with bases around 4000-5000 ft. It should
be more unstable today, and scattered SHRA and TSRA are expected to
develop from mid-afternoon thru the evening hours. Winds should
shift out of the SW, but remain fairly light.

Elsewhere: VFR expected outside mountain valleys, where IFR fog is
developing early this morning. Winds will remain light WSW  or calm
thru daybreak, then increase slightly out of the SW, except NW at
KAVL. A Low-VFR-level cumulus field should around midday. Isolated
to scattered SHRA and TSRA from mid-afternoon thru the evening will
warrant a PROB30 at all terminals.

Outlook: Primarily afternoon and evening TSRA are possible each
day, bringing periodic restrictions. Areas of morning fog and/or
low stratus may potentially develop especially where RA fell the
previous evening. This pattern will continue through at least the
end of the work week.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       Med   77%     High 100%     High 100%     High  98%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  85%     High  84%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:




AVIATION...ARK is the U.S. government's official web portal to all federal, state and local government web resources and services.